Articles tagged with sonorus

  1. SONORUS meeting in Naples

    Two weeks ago there was a SONORUS meeting and school in Naples and Sorrento, Italy. The topic of the school was 'Computational Soundscape Analysis'. The next meeting will be in October in Gothenburg, Sweden.

  2. Paper at Euronoise

    The timetable for Euronoise 2015 is available. I will present the paper Determining an Empirical Emission Model for the Auralization of Jet Aircraft on Tuesday the second at nine in the morning.

    Update

    Seems like my presentation is moved to 10:20.

  3. Auralization: Doppler effect

    Notebook
  4. Research visit to Chalmers

    After the ASA meeting in Indianapolis I went to Gothenburg again for a research visit. As I wrote in my previous post it was strange to be there again. Last spring I visited Gothenburg for just a couple of days, but now, staying for seven weeks again is quite different. You start noticing quite a lot of things have changed. Many people I knew there have moved away and I also noticed a couple of restaurants I visited have closed since. Despite those things it was nice meeting old friends again.

    So, as I wrote in the title I went there on a research visit. The main reason for my visit was to attend some courses at Chalmers but to also work on my research. Initially the idea was to investigate further the model we're developing to deal with atmospheric turbulence in aircraft auralisations. However, in the end the courses took more time then I expected, so I didn't really get to work on the turbulence model anymore. However, I did manage to implement one nice part of the auralisation tool, namely support for Ambisonics.

    Besides Chalmers I also visited SP in Borås. SP was a familar place for me as well since I did an internship there in 2010. Earlier I had made recordings with a SoundField microphone, however, at Empa we do not have an Ambisonics setup. SP has a listening room with a third order Ambisonics system, giving me the possibility to listen to the first order recording as well as to higher order auralisations.

    One visit I met up with Peter Lundén who installed the system. After some problem solving we managed to get both the recordings and auralisations working. Unfortunately there was one problem with the auralisations, somehow halfway the aircraft makes a U-turn. While I haven't checked it any further, I think it is due to the inclusion of the Condon-Shortley phase in the function I used to calculate the spherical harmonics.

  5. Forum Acusticum 2014, Krakow

    Last week the conference Forum Acusticum 2014 took place in the city of Krakow, Poland. From Monday till Friday there were presentations as well as meetings of technical committees. The presentations covered a wide range of topics like structural acoustics, human response and auralisation.

    A special session was organised on Urban Sound Planning as well, in which many of my project members presented their current work. I'm glad a lot of people attended the session.

    I gave a presentation with the title Modelling sound propagation in the presence of turbulence for the auralisation of aircraft noise in a session on Environmental Acoustics. This session was Friday morning early, which was a bit unfortunate, considering there was a nice party with the Young Acousticians Network the evening before. I was surprised there were still so many people that morning!

    On Thursday I joined a discussion on benchmarking for computational acoustics. When implementing a model you would like to be able to validate this. This can sometimes be difficult due to lack of available information or benchmarks. Therefore, the idea is now to put online some kind of repository where people can put their benchmarks. Considering this is a topic of interest in other fields of science I am really curious how they deal with this.

    The city of Krakow surprised me a lot. It's quite a green city and there seems to be a good and relaxed mood. There's plenty of pubs and restaurants, especially around the main square which is huge.

    Anyway, that's my summary on FA2014!

  6. Back in Gothenburg for SONORUS

    Last month I was back in Gothenburg for a week and it was nice! I've been living in Gothenburg for close to two years and being back there brought up some good memories. The reason I was there again was that we had a course for SONORUS on leadership.

    In the course we treated topics like communication, knowledge, coaching, group dynamics and decision making. There was one very interesting exercise on group dynamics. In 20 minutes the entire group had to agree on a list of statements related to meetings. We also built a tower using dry spaghetti, a meter of tape and a marshmallow, or at least we tried!

    Besides the course we spent time on some practical matters in the project, like discussing how we would cooperate, e.g. with regards to sharing data. Another topic that was discussed is the upcoming International Noise Awareness Day, but more about that later!

  7. Modelling a turbulent atmosphere

    When listening to an aircraft flying over, you can hear that the level and spectral contents fluctuate somewhat. These fluctuations are due to turbulence in the atmosphere, affecting the sound generation (variable load on engines) and the sound propagation. In order to create a plausible auralisation of aircraft noise these fluctuations have to be accounted for.

    Turbulent flow can be modeled as a superposition of a spectrum of fluctuations and eddies upon a mean flow. A common approach for noise predictions methods to include the effects of atmospheric turbulence is to use a statistical approach; generate many random 'frozen' turbulence fields, calculate for each of these how sound propagates through them and then average your results. The 'frozen' fields represent snapshots in time of how the atmosphere could look like. These snapshots are calculated based on a spectrum of fluctuations. Well known descriptions of these spectra are the Gaussian and von Karman spectra.

    The figure belows shows a portion of two turbulence spectra.

    Gaussian and Von Karman spectral densities as function of wavenumber.

    A random turbulence field is created by the superposition of modes. The figure below shows the amplitude of these modes as function of wavenumber.

    Gaussian and Von Karman mode amplitudes as function of wavenumber.

    And finally a figure showing the refractive-index fluctuation. The field is generated using a Von Karman spectrum and 200 modes.

    Von Karmann refractive-index field.

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